Investigation of secondary neutron dose for 18 MV dynamic MLC IMRT delivery
Investigation of secondary neutron dose for 18 MV dynamic MLC IMRT delivery
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DOI：
10.1118/1.1861162
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发表时间：
2005-03-01
期刊：
影响因子：
3.8
通讯作者：
Fullerton, GD
中科院分区：
文献类型：
--
作者：
Howell, RM;Ferenci, MS;Fullerton, GD
比较了 18 MV 常规放射治疗和调强放射治疗 (IMRT) 治疗计划的二次中子剂量。 IMRT 使用动态多叶准直 (MLC) 进行。使用静态 MLC 进行额外测量，使用的主准直视场尺寸为 10 x 10 cm(2)，MLC 视场尺寸为 0 x 0、5 x 5 和 10 x 10 cm(2)。测量中子谱并计算有效剂量。 IMRT 治疗导致更高的中子注量和更高的剂量当量。这些增加大约是监视器单元的比率。将静态 MLC 测量与蒙特卡罗计算进行比较。 Varian Clinac 2100/2300C（包括 MLC）的实际组件尺寸和材料使用 MCNPX 进行建模，以计算治疗头内部和周围产生的中子注量。 10 x 10 cm(2) 准直场尺寸与 0 x 0 cm(2) MLC 场的计算值和测量值之间存在极好的一致性。对于这种几何结构，探测器位置处的大多数中子直接来自加速器头，其中少量来自房间散射。未来的研究需要调查 IMRT 中使用的不同束能量的影响，结合散射光子剂量和二次中子剂量的影响。 (c) 2005 年美国医学物理学家协会。
Secondary neutron doses from the delivery of 18 MV conventional and intensity modulated radiation therapy (IMRT) treatment plans were compared. IMRT was delivered using dynamic multileaf collimation (MLC). Additional measurements were made with static MLC using a primary collimated field size of 10 x 10 cm(2) and MLC field sizes of 0 x 0, 5 x 5, and 10 x 10 cm(2). Neutron spectra were measured and effective doses calculated. The IMRT treatment resulted in a higher neutron fluence and higher dose equivalent. These increases were approximately the ratio of the monitor units. The static MLC measurements were compared to Monte Carlo calculations. The actual component dimensions and materials for the Varian Clinac 2100/2300C including the MLC were modeled with MCNPX to compute the neutron fluence due to neutron production in and around the treatment head. There is excellent agreement between the calculated and measured neutron fluence for the collimated field size of 10 x 10 cm(2) with the 0 x 0 cm(2) MLC field. Most of the neutrons at the detector location for this geometry are directly from the accelerator head with a small contribution from room scatter. Future studies are needed to investigate the effect of different beam energies used in IMRT incorporating the effects of scattered photon dose as well as secondary neutron dose. (c) 2005 American Association of Physicists in Medicine.